The last several years have witnessed significant advances in the field of plastic electronics (i.e. light-emitting diodes, photovoltaic devices, biosensors, etc.). The availability of simple and reliable coupling procedures (i.e. Stille, Suzuki, Heck, Kumada, etc.) to afford well-defined and reproducible polymeric materials is directly linked to the many advances in the field of plastic electrodes. However, these state-of-the-art methods generally involve organometallic reagents which create metal waste and require additional synthetic steps and more extensive purification procedures.
The Stille cross-coupling reaction has allowed significant advances in the synthesis of new organic molecules.[1] This reaction also had a significant impact in the field of macromolecular chemistry, especially regarding the synthesis of conjugated polymers.[1,2] However, notwithstanding its great versatility, the Stille reaction involves drawbacks such as the formation of toxic tin by-products and in some cases, instability of the organometallic reagents.
Recently, the development of reactions called “direct arylation” has received much attention.[3] These reactions allow the formation of carbon-carbon bonds between aromatics units with activated hydrogen atoms without the use of organometallic intermediates. Actually, these reactions are mostly developed for the synthesis of small molecules.[4] Indeed, up to now, only a few publications reported the use of direct arylation in polymerization reactions.[5] Moreover, there are very few examples showing the coupling between thiophenes or thiophene derivatives via direct heteroarylation and these moieties are particularly important monomers for plastic electronics.
The thieno[3,4-c]pyrrole-4,6-dione (TPD) unit is a useful building block for the development of new conjugated polymers for organic solar cells (power conversion efficiencies up to 7.3%)[6] and more recently, for organic field-effect transistors (hole mobilities up to 0.6 cm2V−1s−1).[7]
Despite the many synthetic procedures available, the development of greener and cheaper synthetic procedures is desired. Greener materials are likely to exhibit improved performance and stability, considering they are inherently cleaner (absence of organometallic by-products). One promising approach is merging the advantages of plastic solar cells with new ecofriendly synthetic procedures. However, little is known about the production of green energy from green materials.